Spatial variation in the strength of herbivore top-down control represents an important source of variation in plant fitness measures and community structure and function. By measuring seed predator (larvae of a Noctuid moth) and parasitoid impacts on Ruellia nudiflora across a broad spatial scale in Yucatan (Mexico), this study addressed the following: (1) to what extent does seed predator and parasitoid attack intensity associated with R. nudiflora vary spatially? (2) Does parasitoid attack result in a positive indirect effect on the plant, and does the intensity of this effect vary spatially? During the peak of fruit production (late June-early July) of 2005, we collected fruits from 21 R. nudiflora populations and grouped them into four regions: center, east, north and south. For each fruit we recorded: observed seed number, number of seeds eaten, seed predator presence, parasitoid presence and number of seeds 'saved' by parasitoids. Seed predators attacked ca 30 percent of fruits/plant on average, while parasitoids were found in 24 percent of seed predator-attacked fruits. Results indicated spatial variation in seed predator and parasitoid attack levels; interestingly, a contrasting spatial gradient of attack intensity was observed: populations/regions with greatest parasitoid attack levels usually had the lowest seed predator attack levels and vice versa, suggesting top-down control of parasitoids on seed predators. We observed a weak overall indirect impact of parasitoids on R. nudiflora (4% seeds 'saved' on average), which nonetheless varied strongly across populations (e.g., close to 14% seeds saved at one population). Findings indicate a geographical structuring of interaction strengths across populations, as well as spatial variation in the strength of parasitoid cascading effects on plant reproduction. Abstract in Spanish is available at

1. Dung beetles provide recognised environmental services in cattle production systems, but can be negatively affected by the pharmaceutical residues found in excreta, particularly macrocyclic lactones (ML).2. The diversity and seasonal abundance of dung beetle communities were measured using baited pitfall traps and compared at four cattle ranches in Yucatan, Mexico, to assess the possible effects of ML residues. Cattle parasite control was performed at two of these ranches using ML.3. A total of 93 274 dung beetles from 17 species were collected. The dominant species at all four ranches were Onthophagus landolti and Canthon indigaceus chevrolati. Compared to ranches where ML was not used, total abundance was higher but richness, evenness and diversity were lower at ranches where ML was used. Five other species were identified as potential indicator species for determining whether there was an effect of ML use at the studied ranches.4. Seasonal patterns differed between beetle communities: those found at non-ML sites occurred in higher abundances in May and July, while those at ML sites had higher abundances in May and June. This was probably because herds on ML sites were treated with ML to control parasites in early July.5. The application of ML for controlling cattle parasites was shown to have a negative effect on the diversity and abundance of dung beetles. These results emphasise the need for timing ML use in order to mitigate the adverse impacts on these insects.

Previous work has documented toxic effects of ivermectin (IVM) on dung beetles from the Old World, but very little is known about this drug's effect on Neotropical dung beetles. Accordingly, we conducted a bioassay with dung spiked with IVM to assess its lethal and sublethal effects on the Neotropical dung beetle Onthophagus landolti Harold. The experimental design consisted of five treated groups G1, G2, G3, G4, and G5 receiving 0.001, 0.01, 0.1, 1.0, and 10 mg IVM/kg dung fresh weight, respectively, and two control groups (solvent control [CGA] and untreated control [CGU]). Adult survival and fecundity were measured throughout a 10-d period, and subsequent egg development and survival were monitored. Adult survival was only affected for treatment groups G4 and G5 groups (70 and 30%, respectively); groups G1, G2, G3 and both controls exhibited 100% survival. Fecundity was completely suppressed under treatment groups G4 and G5. Group G3 only had 1.7 and 2.1% brood mass production relative to CGA and CGU, respectively. Additionally, for groups G1 and G2 the proportion of adults emerging from brood masses was lower relative to CGA. Furthermore, development time for the second generation in groups G1 and G2 was 12.5% slower relative to control groups. Finally, dung removal by beetles from groups G3, G4, and G5 was significantly lower relative to control groups. In conclusion, toxic effects of IVM on O. landolti are associated mainly with reduced fecundity and lower dung-removal by adult beetles as well as reduced survival and slower development of offspring.

We conducted a baseline characterization of the abundance and seasonality of Aedes aegypti (Linnaeus, 1762)—a vector of dengue, chikungunya, and Zika—in two suburban localities of Yucatan, Mexico, as the first step in the implementation of an integrated vector management (IVM) plan combining ‘traditional Aedes control’ (source reduction/truck-mounted ultra-low volume [ULV] spraying) and incompatible insect technique/sterile insect technique for population suppression in Yucatan, Mexico. Weekly entomological collections with ovitraps and BG-sentinel traps were performed in 1-ha quadrants of both localities for 1 yr. Three distinct periods/phases were identified, closely associated with precipitation: 1) a phase of low population abundance during the dry season (weekly average of Aedes eggs per ovitrap and adults per BG trap = 15.51 ± 0.71 and 10.07 ± 0.88, respectively); 2) a phase of population growth and greatest abundance of Aedes (49.03 ± 1.48 eggs and 25.69 ± 1.31 adults) during the rainy season; and finally 3) a phase of decline among populations (20.91 ± 0.97 eggs and 3.24 ± 0.21 adults) after the peak of the rainy season. Seasonal abundance and dynamics of Ae. aegypti populations suggest that it is feasible to develop and implement time-specific actions as part of an IVM approach incorporating integrating novel technologies (such as rear-and-release of Wolbachia-infected males) with classic (insecticide-based) approaches implemented routinely for vector control. In agreement with the local vector control program, we propose a pilot IVM strategy structured in a preparation phase, an attack phase with traditional vector control, and a suppression phase with inundative releases, which are described in this paper.

No abstract

Background The integration of house-screening and long-lasting insecticidal nets, known as insecticide-treated screening (ITS), can provide simple, safe, and low-tech Aedes aegypti control. Cluster randomised controlled trials in two endemic localities for Ae. aegypti of south Mexico, showed that ITS conferred both, immediate and sustained (~2 yr) impact on indoor-female Ae. aegypti infestations. Such encouraging results require further validation with studies quantifying more epidemiologically-related endpoints, including arbovirus infection in Ae. aegypti. We evaluated the efficacy of protecting houses with ITS on Ae. aegypti infestation and arbovirus infection during a Zika outbreak in Merida, Yucatan, Mexico. Methodology/Principal findings A two-arm cluster-randomised controlled trial evaluated the entomological efficacy of ITS compared to the absence of ITS (with both arms able to receive routine arbovirus vector control) in the neighbourhood Juan Pablo II of Merida. Cross-sectional entomological surveys quantified indoor adult mosquito infestation and arbovirus infection at baseline (pre-ITS installation) and throughout two post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over one year (2016–2017). Household-surveys assessed the social reception of the intervention. Houses with ITS were 79–85% less infested with Aedes females than control houses up to one-year PI. A similar significant trend was observed for blood-fed Ae. aegypti females (76–82%). Houses with ITS had significantly less infected female Ae. aegypti than controls during the peak of the epidemic (OR = 0.15, 95%CI: 0.08–0.29), an effect that was significant up to a year PI (OR = 0.24, 0.15–0.39). Communities strongly accepted the intervention, due to its perceived mode of action, the prevalent risk for Aedes-borne diseases in the area, and the positive feedback from neighbours receiving ITS. Conclusions/Significance We show evidence of the protective efficacy of ITS against an arboviral disease of major relevance, and discuss the relevance of our findings for intervention adoption.

Two bioassays were conducted in parallel to assess the effects of cattle treated with either 1% ivermectin (IVM) or 3.15% IVM (dosed at 0.2 and 0.63 mg kg-1, respectively) on reproduction and survival of Onthophagus landolti Harold. Adult beetles were exposed 10 days to faeces of treated cattle starting at: one day before treatment (controls), 3, 6, 14, 28 and 35 days post-treatment. Adult survival of O. landolti was not affected by either of the two treatments. Faecal residues of 1% IVM almost completely suppressed fecundity of beetles at 3, 6 and 14 days post-treatment (dPT), and reduced fecundity of O. landolti at 28 dPT ( 38.3%), relative to controls. Meanwhile, IVM residues after treatment with 3.15% IVM almost completely suppressed fecundity of beetles at 3, 6, 14 and 28 dPT, and reduced fecundity of O. landolti at 35 dPT (80.9%), relative to controls. Larval survival was significantly reduced only at 3 dPT with 1% IVM. Meanwhile, treatment with 3.15% IVM significantly reduced larval survival at 6, 14 and 28 dPT. Larval mortality was recorded only in L-I and L-II instars. Moreover, in both bioassays, most of the L-I and L-II specimens that survived showed signs of toxicity. In conclusion, residual IVM in cattle faeces after treatment with injectable IVM has a detrimental effect on the fecundity of adult O. landolti up to 4 weeks post-treatment and on the subsequent larval survival.

Scarabaeinae are sensitive to structural habitat changes caused by disturbance. We compared copronecrophagous beetle (Scarabaeinae) community structure in three differently managed zones within an agroecosystem of the northern Yucatan Peninsula, Mexico. We placed dung and carrion traps once a month from June 2004 through May 2005. The beetle community included 17 species from the genera Canthon, Canthidium, Deltochilum, Pseudocanthon, Malagoniella, Onthophagus, Phanaeus, Copris, Uroxys, Sisyphus and Ateuchus. The secondary vegetation had a higher beetle diversity than the other two zones. Species richness was highest in the Brosimum alicastrum plantation. The pasture had the lowest species diversity and richness, but exhibited the highest abundance of Scarabaeinae in the dry season. The two zones with extensive tree cover were the most diverse. Roller beetles were dominant over burrower species and small-sized species outnumbered large species. Our data show two important issues: beetle species in the pasture extended their activity to the beginning of the dry season, while abundances dropped in the other, unirrigated zones; and the possibility that the Scarabaeinae living in neotropical forests are opportunistic saprophages and have specialized habits for resources other than dung. The B. alicastrum plantation is beneficial to the entire ranch production system because it functions as a dispersion and development area for stenotopic species limited to tree cover.